I keep a couple of Ornates, 19" and 12". My experience with them is mine tended to be more aggressive when given places to hide. They seem to want to protect the space. when I say aggressive I mean with other Bichirs. When I kept them in open space nowhere to hide the aggression went away. This is just my own experience. I keep them in my main tank, 300g with all my other fish that also include big Endlis Congicus Koliba Ansorgi Have had no problems with them biting the other Bichirs. Course if want decor in your tank they will hide a lot. I think you could keep one without any other bichirs.
not long left i'll post pics when its here. The wait is going to kill me